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Question
compound microscope consists of two convex lenses of focal length 2 cm and 5 cm. When an object is kept at a distance of 2.1 cm from the objective, a virtual and magnified image is fonned 25 cm from the eye piece. Calculate the magnifying power of the microscope.
Solution
For objective lens (L0 ) u0=-2.1cm
f0 = 2 cm
`1/(f_0)=1/(v_0) -1/(u_0)`
⇒ `1/2 = 1/(v_0) +1/2.1`
⇒ `1/(v_0) = 1/2 - 1/(2.1) = (2.1-2)/(4.2) = 1/42` cm
v0 = 42 cm
Magnifying ower = `(v_0)/(u_0) (1+D/(f_e))`;
[∵ Magnified image is formed 25 cm i.e., least distance ]
Magnifying power = `42/(-2.1)(1+25/5)=-45/(2.1) xx6`
Magnifying power = -120
negative sign shows the final image is inverted
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